Researchers develop robust biopolymer network binder enabling high sulfur loading in Li-S electrodes
Researchers from China and Australia have developed a mechanically robust biopolymer network binder that enabled the preparation of high-loading sulfur electrodes to improve the electrochemical performance of Li-sulfur batteries. The binder supported a high-sulfur-loading electrode of 19.8 mg cm-2 with an ultrahigh areal specific capacity of 26.4 mAh cm-2.
The network binder effectively prevented polysulfides within the electrode from shuttling and, consequently, improved electrochemical performance. This study, published in the RSC journal Energy & Environmental Science, identifies a new way to obtaining high-energy-density batteries by the simple application of robust network biopolymer binders that are inherently low-cost and environmentally friendly.
|Cycling performance of sulfur cathodes with different binders with sulfur loading of 6.5 mg cm-2 at 0.8 mA cm-2. N-GG-XG is the biopolymer network binder under study. Liu et al. Click to enlarge.|
Developing high-loading electrode is an effective way to increase areal capacity and thus energy density of batteries. However, as the amount of areal loading increases, electrode film on current collector becomes thicker. The thick electrode tends to fracture and delaminate from current collector after coating and drying, making the high-loading electrode much difficult to be realized. Moreover, the issues of lithium-sulfur (Li-S) battery, including formation of soluble long-chain polysulfides, which easily diffuse out of the cathode scaffold and cause shuttle reaction, insulator nature of sulfur material, and huge volume change (76%) during charge and discharge, become much more serious in high-loading Li-S battery.
Only when applying well-designed electrode structure, high-loading Li-S battery could be obtained. Three-dimensional (3D) porous current collectors, layer-by-layer structured electrodes, and functional separators were exploited to realize high-loading Li-S batteries. Among them, the highest areal capacity of 23.3 mAh cm-2 with a sulfur loading of 21.2 mg cm-2 was obtained; however, these reported well-designed electrode structures used complicated preparation process and were difficult for widespread applications.
… we propose that high-energy-density battery with high-loading active material can be achieved by simply exploiting an effective binder.—Liu et al.
The team constructed the mechanically robust 3D network binder by weaving dual biopolymers (guar gum and xanthan gum, denoted as N-GG-XG binder) via an intermolecular binding effect through extensive functional groups of both polymers.
Both biopolymers are non-toxic, low cost, sustainable natural products. Both also contain large numbers of oxygen-containing functional groups, which can effectively bind polysulfides.
Further, the binder facilitates electrode fabrication in a water-based process.
It is for the first time, to the best of our knowledge, to realize such high-loading Li-S battery by simply applying a polymer binder.—Liu et al.
Jie Liu, Dilini G. D. Galpaya, Lijing Yan, Minghao Sun, Zhan Lin, Cheng Yan, Chengdu Lianga and Shanqing Zhang (2016) “Exploiting a robust biopolymer network binder for an ultrahigh-areal-capacity Li–S battery” Energy Environ. Sci. doi: 10.1039/C6EE03033E